Copyright 2020 Peter Tribble
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flowadm add-flow [-t] [-R root-dir] -l link -a attr=value[,...] [-p prop=value[,...]] flow flowadm remove-flow [-t] [-R root-dir] {-l link | flow} flowadm show-flow [-p] [-l link] [-o field[,...]] [flow]
flowadm set-flowprop [-t] [-R root-dir] -p prop=value[,...] flow flowadm reset-flowprop [-t] [-R root-dir] [-p prop[,...]] flow flowadm show-flowprop [-cP] [-l link] [-o field[,...]] [-p prop[,...]] [flow]
The flowadm command allows users to manage networking bandwidth resources for a transport, service, or a subnet. The service is specified as a combination of transport and local port. The subnet is specified by its IP address and subnet mask. The command can be used on any type of data link, including physical links, virtual NICs, and link aggregations.
A flow is defined as a set of attributes based on Layer 3 and Layer 4 headers, which can be used to identify a protocol, service, or a virtual machine. When a flow is identified based on flow attributes, separate kernel resources including layer 2, 3, and 4 queues, their processing threads, and other resources are uniquely created for it, such that other traffic has minimal or zero impact on it.
Inbound and outbound packet are matched to flows in a very fast and scalable way, so that limits can be enforced with minimal performance impact.
The flowadm command can be used to define a flow without imposing any bandwidth resource control. This would result in the traffic type getting its own resources and queues so that it is isolated from rest of the networking traffic for more observable and deterministic behavior.
flowadm is implemented as a set of subcommands with corresponding options. Options are described in the context of each subcommand.
Adds a flow to the system. The flow is identified by its flow attributes and properties. As part of identifying a particular flow, its bandwidth resource can be limited and its relative priority to other traffic can be specified. If no bandwidth limit or priority is specified, the traffic still gets its unique layer 2, 3, and 4 queues and processing threads, including NIC hardware resources (when supported), so that the selected traffic can be separated from others and can flow with minimal impact from other traffic. -t, --temporary
The changes are temporary and will not persist across reboots. Persistence is the default.
Specifies an alternate root directory where flowadm should apply persistent creation.
Specify the link to which the flow will be added.
A mandatory comma-separated list of attributes to be set to the specified values.
An optional comma-separated list of properties to be set to the specified values. Flow properties are documented in the "Flow Properties" section, below.
Remove an existing flow identified by its link or name. -t, --temporary
The changes are temporary and will not persist across reboots. Persistence is the default.
Specifies an alternate root directory where flowadm should apply persistent removal.
If a link is specified, remove all flows from that link. If a single flow is specified, remove only that flow.
Show flow configuration information, either for all flows, all flows on a link, or for the specified flow. -o field[,...]
A case-insensitive, comma-separated list of output fields to display. The field name must be one of the fields listed below, or a special value all, to display all fields. For each flow found, the following fields can be displayed: flow
The name of the flow.
The name of the link the flow is on.
IP address of the flow. This can be either local or remote depending on how the flow was defined.
The name of the layer for protocol to be used.
Local port of service for flow.
Remote port of service for flow.
Differentiated services value for flow and mask used with DSFIELD value to state the bits of interest in the differentiated services field of the IP header.
Display using a stable machine-parsable format.
Display persistent flow property information.
Display information for all flows on the named link or information for the named flow.
Set values of one or more properties on the flow specified by name. The complete list of properties can be retrieved using the show-flowprop subcommand. -t, --temporary
The changes are temporary and will not persist across reboots. Persistence is the default.
Specifies an alternate root directory where flowadm should apply persistent setting of properties.
A comma-separated list of properties to be set to the specified values.
Resets one or more properties to their default values on the specified flow. If no properties are specified, all properties are reset. See the show-flowprop subcommand for a description of properties, which includes their default values. -t, --temporary
Specifies that the resets are temporary. Temporary resets last until the next reboot.
Specifies an alternate root directory where flowadm should apply persistent setting of properties.
A comma-separated list of properties to be reset.
Show the current or persistent values of one or more properties, either for all flows, flows on a specified link, or for the specified flow. By default, current values are shown. If no properties are specified, all available flow properties are displayed. For each property, the following fields are displayed: FLOW
The name of the flow.
The name of the property.
The current (or persistent) property value. The value is shown as -- (double hyphen), if it is not set, and ? (question mark), if the value is unknown. Persistent values that are not set or have been reset will be shown as -- and will use the system DEFAULT value (if any).
The default value of the property. If the property has no default value, -- (double hyphen), is shown.
A comma-separated list of the values the property can have. If the values span a numeric range, the minimum and maximum values might be shown as shorthand. If the possible values are unknown or unbounded, -- (double hyphen), is shown.
Display using a stable machine-parsable format.
Display persistent flow property information.
A comma-separated list of properties to show.
Identifies a network flow by the local IP address. value must be a IPv4 address in dotted-decimal notation or an IPv6 address in colon-separated notation. prefix_len is optional. If prefix_len is specified, it describes the netmask for a subnet address, following the same notation convention of ifconfig(8) and route(8) addresses. If unspecified, the given IP address will be considered as a host address for which the default prefix length for a IPv4 address is /32 and for IPv6 is /128.
Identifies a network flow by the remote IP address. The syntax is the same as the local_ip attribute.
Identifies a layer 4 protocol to be used. It is typically used in combination with local_port to identify the service that needs special attention.
Identifies a service specified by the local port.
Identifies a service specified by the remote port.
Identifies the 8-bit differentiated services field (as defined in RFC 2474). The optional dsfield_mask is used to state the bits of interest in the differentiated services field when comparing with the dsfield value. A 0 in a bit position indicates that the bit value needs to be ignored and a 1 indicates otherwise. The mask can range from 0x01 to 0xff. If dsfield_mask is not specified, the default mask 0xff is used. Both the dsfield value and mask must be in hexadecimal.
The following six types of combinations of attributes are supported:
local_ip=address[/prefixlen] remote_ip=address[/prefixlen] transport={tcp|udp|sctp|icmp|icmpv6} transport={tcp|udp|sctp},local_port=port transport={tcp|udp|sctp},remote_port=port dsfield=val[:dsfield_mask]
On a given link, the types of combinations above are mutually exclusive. An attempt to create flows of different types on a given link will fail.
An attribute can be listed only once for each flow. For example, the following command is not valid:
# flowadm add-flow -l vnic1 -a local_port=80,local_port=8080 httpflow
transport and local_port:
TCP, UDP, or SCTP flows can be specified with a local port. An ICMP or ICMPv6 flow that specifies a port is not allowed. The following commands are valid:
# flowadm add-flow -l e1000g0 -a transport=udp udpflow # flowadm add-flow -l e1000g0 -a transport=tcp,local_port=80 \e udp80flow
The following commands are not valid:
# flowadm add-flow -l e1000g0 -a local_port=25 flow25 # flowadm add-flow -l e1000g0 -a transport=icmpv6,local_port=16 \e flow16
Sets the full duplex bandwidth for the flow. The bandwidth is specified as an integer with one of the scale suffixes(K, M, or G for Kbps, Mbps, and Gbps). If no units are specified, the input value will be read as Mbps. The default is no bandwidth limit.
Sets the relative priority for the flow. The value can be given as one of the tokens high, medium, or low. The default is medium.
The command below creates a policy around inbound HTTPS traffic on an HTTPS server so that HTTPS obtains dedicated NIC hardware and kernel TCP/IP resources. The name specified, https-1, can be used later to modify or delete the policy.
# flowadm add-flow -l bge0 -a transport=TCP,local_port=443 https-1 # flowadm show-flow -l bge0 FLOW LINK IPADDR PROTO LPORT RPORT DSFLD https1 bge0 -- tcp 443 -- --
Example 2 Modifying an Existing Policy to Add Bandwidth Resource Control
The following command modifies the https-1 policy from the preceding example. The command adds bandwidth control and give the policy a high priority.
# flowadm set-flowprop -p maxbw=500M,priority=high https-1 # flowadm show-flow https-1 FLOW LINK IPADDR PROTO LPORT RPORT DSFLD https-1 bge0 -- tcp 443 -- -- # flowadm show-flowprop https-1 FLOW PROPERTY VALUE DEFAULT POSSIBLE https-1 maxbw 500 -- -- https-1 priority high -- low,medium,high
Example 3 Limiting the UDP Bandwidth Usage
The following command creates a policy for UDP protocol so that it cannot consume more than 100Mbps of available bandwidth. The flow is named limit-udp-1.
# flowadm add-flow -l bge0 -a transport=UDP -p maxbw=100M, \e
priority=low limit-udp-1
Example 4 Setting Policy, Making Use of dsfield Attribute
The following command sets a policy for EF PHB (DSCP value of 101110 from RFC 2598) with a bandwidth of 500 Mbps and a high priority. The dsfield value for this flow will be 0x2e (101110) with the dsfield_mask being 0xfc (because we want to ignore the 2 least significant bits).
# flowadm add-flow -l bge0 -a dsfield=0x2e:0xfc \e
-p maxbw=500M,priority=high efphb-flow
All actions were performed successfully.
An error occurred.
| ATTRIBUTE TYPE ATTRIBUTE VALUE |
| Interface Stability Committed |